A coodinated effort is planned to acquire greater understanding of the events involved in the development and specification of neural connections, the factors governing their stability, and the trophic, inductive influences exerted by one cell on another. These projects fall into four areas: (a) assessment of the trophic and inductive effectts of nerves of different types on skeletaa muscle, in particular a study of the synapses formed by preganglionic autonomic nerves on frog skeletal muscle; andcompetition between these nerves and more appropriate somatic motor nerves; (b) an analysis of the influence of nerve and muscle inactivity in chick embryos, and the role of he nerve, if any, in determining the fate of genetically dystrophic muscle tissue; (c) the role of nerve integrity, activity and axoplasmic transport will be analyzed in mammlian neuromuscular preparation, with emphasis on the final effects of denervation; (d) determination of the plasticity of respecification of retino-tectal connections in fish, coupled with behavioral analysis of the degree of function restored in cases of "compressed" optic nerve projection. A variety of tectal and retinal lesions, including tectal rotation, are planned as challenges to the system.